Google does not always work.-----The impeller is on the propshaft , right in front of the propeller.----Take the prop off and have a good look in and around that area.
Put some oil into the lower crankcase.----See if it pours out the bottom seal.-----Hard to tell but in picture #3 the seal looks iffy in the 6:30 / 7:00 o-clock area.
Charge battery.----Have battery load tested.-----Take starter apart for inspection .---Do ohm check on armature.-----If flywheel spins too slow there will be no spark.
The electric primer is NOT a pump, it is a valve.----If the valve is open the motor will flood and die.-----I suggest you look into cleaning the VST tank.
Check to see if spark will jump a gap of 7/16".----Note---The sparkplugs have nothing to do with that test !----The jets ( orifice plugs ) are easy to remove from the carburetors.-----Post the numbers you find on the high and low speed jets.---No need to remove carburetors to get those numbers.